Field of the Invention
The present invention relates to an input state detection device for detecting contact or pressing of an electrically conductive object such as a human finger.
Description of the Related Art
A patent Literature 1(PL1) describes a device capable of detecting approach and pressing of a human finger by using an electrostatic capacitive sensor. As a finger approaches a first electrode, variable capacitance increases. In addition, as the first electrode and a second electrode get closer to each other by the finger's pressing the first electrode by way of an electrically insulating sheet, the variable capacitance increases. Detection of touch of the finger and detection of pressing of the finger are carried out by monitoring a change in potential or electric current of the first electrode and a change in potential or electric current of the second electrode.
PL1: JP2010-217967A
Here, in a detection circuit described in Patent Literature 1, potential or an electric current detected when a finger presses the first electrode is affected by a change in potential or electric current of a side of the first electrode and a change in potential or electric current of a side of the second electrode. Therefore, there is a risk that the detected potential or electric current is unstable depending magnitude of pressing force.
The present invention has been made in view of these circumstances. It is an object of the present invention to provide an input state detection device capable of reliably detecting contact and pressing of an object.